So I’ve added a new CC2531 pre-flashed as a co-ordinator.
I’ve added the Mosquitto Broker add on, created a new user and installed the MQTT integration, selected auto discover, all as per the documentation.
However, I’ve removed a Hue motion sensor from the Hue hub, reset it but it’s not showing in the MQTT integration as a device.
Am I missing a step or two in my set up of MQTT?
Also, how does the integration/add-on know to use the new user I created specifically for MQTT? I’m confused!
So at a guess you’re using zigbee2mqtt?
Is it running? Did it pair OK with zigbee2mqtt? Can you see the device in the zigbee2mqtt web UI? If so what is it called there?
Marc, I’m obviously missing something in my set up because I don’t know about pairing the coordinator or the zigbee2mqtt web UI.
I just followed videos that showed the coordinator simply needed plugging into the RPi.
In order for your zigbee device to to speak to homeassistant you need to use a method to ‘translate’ (for want of a better word) what the zigbee device is saying so that homeassistant can understand it.
There are three options. Zigbee2mqtt, zha and deconz.
Zha is a homeassistant component that can talk to your zigbee devices via the dongle, but as far as I know does not use mqtt.
Zigbee2MQTT is third party software, but many people (myself included) use it as its so good. You can run the software as a homeassistant addon, and what it does is speak to your zigbee devices via your dongle and then communicates with homeassistant via mqtt.
Deconz I don’t know much about, other than to say it is also quite popular and is mentioned a fair bit.
I think you need to have a read up on ways to communicate between homeassistant and zigbee, decide which way you want to do it, and then find some ‘getting started’ instructions for that method.
The zigbee2mqtt docs are here…
The homeassistant zha docs are here…
You’ll have to google deconz 
Got it working now via the zigbee2mqtt add on.
Thanks for your help, Marc.
No worries 